Control of inverse voltage



June 19, 1934. J, B, WAN-rz 1,963,160

CONTROL OF INVERSE VOLTAGE Filed oct. 22, 1928 2 sheets-sheet 1 FIGZFIG,4

QUOIUVOU June 19, 1934. J, B WAN-rz CONTROL 0F INVERSE VOLTAGE 2sheets-sheet l2 Filed OCb. 22, 1928 am n ....f... mb

INI/EN TOR. JUUUS B. WHNTZ AT ORNEY.

Patented June 19, 1934 CONTROL F INVERSE VOLTAGE Julius B. Wantz, OakPark, Ill.,l assigner to General Electric X-Ray Corporation, Chicago,Ill., a corporation of New York Application October 22,

(Cl. ,Z50-f3.4)

Claims.

y operate on alternating current, and in connection therewith, it isusual to generate an alternating current of the proper potential andthen supply mechanical, chemical, or electrical rectifying dev vices.

In some cases these are in the form of separate units but in a number ofcases the energy consuming device embodies in itself the necessaryrectfying function. That is, the device itself is a valve permitting theflow therethrough of elec- 20, trical pulsations, generally referred toas the useful half of the Wave, and rejecting the alternate pulsations,which amounts in such an instance to the undesired or unused portion ofthe wave.

One. of the most important energy consuming devices which is of itself arectifier, is the socalled self-r'ectifying X-ray tube. This tube,because of the design of its electrodes and also because of the highvacuum existing Withinthe en- 3@ 'velope thereof, will only permit `thepassage of'current through it in one direction, on the one hand, passingthe useful alternation of the current wave of the selected polarity andrejecting the remaining half Wave thereof, so that a tube v is energizedby, a pulsating unidirectional current comprising only the alternationsof selected polarity.

The rejected half cycle is generally termed in-l verse, and it performswith an X-ray tubeno use- 40 ful function, but is a distinct detrimentto the operation. of a tube, and provides a factor in problems ofinsulation which must be fully considered in the design of X-rayapparatus intended to be used with such a self -rectifying X-ray tube.

Inpersisting with the discussion of the present invention,A stress islaid upon X-ray apparatus only because that type of apparatus has beenemployed for the purpose of providing an illustrative example of theadvantages to be obtained ,50 by the advances described in thisapplication.

' Great strides have recentlyV been made in the X-ray art due to thefact that the application of oil insulation to both the X-ray tube andenergizing devices has been found highly successful, and

v that such insulation provides advantages to the 1928, Serial No.314,030

operator which cannot be had in any equipment where exposed high tensionWires must be employed. A further discussion of such advantages can bereadily had by referring to copending ap'- pl'ications, one of which isthe application of 60 Julius B. Wantz and Julius J. Grobe, seriallynumbered 286,825 filed June 20, 1928 and entitled X-ray operatingtable'. l

The capacity of any X-ray apparatus of the oil-immersed type, just as isthe case in any other X-ray apparatus', or in any other electricaldevice using high tension electricity, resides in the ability of theengineer designing such apparatus to take care of the problem ofinsulation. This is an immense factor in present day X-ray apparatus,especially that' of the oil-immersed type. For example, self-rectifyingtubes are employed in tanks of limited capacity, the tanks containingtransformer oil for the purpose of insulation. It is the desire of theengineer to avoid increasing theA size of such tank, because theincrease in size will lead to bulkiness and greater Weight which will beobjectionable not only because making the tank unwieldy and cumbersomefrom a standpoint of manipulation but also because such inv0 crease inweight of the X-ray tube and its associated container forces thedesigner to make the supporting mechanism for such containercorrespondingly strong, more expensive and more difcult to manipulate.

It follows then, that it will be to the' material advantage of the X-rayart to avoid a necessity for enlarging the present day type of tankemployed with X-ray tubes and particularly with X-ray tubes of theself-rectifying type when increased electromotive force is impressedtheref upon.

As is readily understood by the electrical engineer, the' potential ofthe useful portion of the vvaveV is less than that of the unusedportion'. This is due to the fact that the useful portion of the' Wavebeing utilized in the X-ray tube i-ts potential is diminished by anamount equal to the voltage drop` in the source of energy which is de'-pendent on the amount of current passing through the X-ray tube. As nocurrent' passes When the inverse half cycle is impressed across the tubethis voltage loss is not present and the' full potential generated bythe source of current is impressed on the X-ray tube. On an oscillo- 10graph diagram made for determining this question, invariably it is shownthat the amplitude of the useful portion of the wave is from ten totwenty percent less than the amplitude of the inverse portion of theWave.

Insulation must be provided to take care of the highest potentialpresent in the apparatus and as the potential of the inverse half waveis from ten to twenty per cent greater than that of the useful part ofthe Wave it is necessary that the X-ray engineer insulate for apotential of greater magnitude than that which is usefully employed ingenerating X-rays. Thus, the present day oil-immersed X-ray apparatus isprovided with insulation adapted to take care of a greater voltage thanthat which is actually used in theX- ray tube contained in theapparatus.

This invention is designed for the express purpose of increasing theuseful load which may be impressed upon an electrical device of givendesign and to increase the capacity of presentl day apparatus for auseful load to the limit of the insulation therein, such insulation now,as previously stated, being in excess of that required to withstand thehighest potential used by the device.

Naturally, and as a consequence of this arrangement, means must beprovided whereby there may be an increase of the potential of the usefulhalf wave, that is, of the amplitude of that part of the voltage wavewhich is used in the device without a corresponding increase in .theamplitude of the unused portion of the wave or the inverse as would bethe case Where the present apparatus is not employed.

This result may be accomplished by reducing ythe potential of theinverse half cycle until it is of an amplitude not greater than theamplitude of the used half cycle. By reducing the amplitude of theinverse until it equals the amp-litude of the used portion of the wave,theI maximum efiiciency of the apparatus for useful work, so far asinsulation is concerned, is attained.

It is not intended that the invention need stop with equalizlng theinverse and the used portion of the Wave, but that it will extend to acomplete control of the inverse whereby it may be regulated so that itspotential is in a selected or desired quantity, approaching zero as alimit.

It will be repeated, that the present invention is applicable to a largenumber of problems of electrical insulation for apparatus, and is in noway conned exclusively to the X-ray art, but is capable of adoption toany type of apparatus re quiring unilateral current and which isenergized directly from a source of alternating current.

Aslmay lbe readily gathered from the remarks hereinabove made, theobjects of the invention, among others include- Means providing for anincrease in the operating potential of vacuum tubes and otherelectricallapparatus which rectify their own current, as well as meansfor reducing the magnitude of the unused portion ofthe electromotiveforce used for energizing such tubes or apparatus.

To provide a device which is adapted to increase operating potential ,ofitself or of an ancillary apparatus and which contains means forselectively absorbing energy from the unused portion of the wave. Y

y To provide means'whereby there Will be absorption of the unused partof a Wave obtained through selective loading.

` To provide adequate means for controlling an electrical device inIwhich is employed unidirectional pulsating energy by selectivelyabsorbing energy from the unused portion of the wave and adjusting suchabsorption with the changes in the load on the apparatus which isenergized by the useful portion of the wave.

A circuit incorporating an energy consuming device operate-d on aselected portion of an electrical impulse and in association with adevice in which insulation must be provided in excess of that requiredfor the used portion of the impulse to prevent breakdown of theinsulation through the strain produced by such unused portion thereofwhereby such strain produced by such unused portion is reduced to permitof the energy of the useful impulse to be correspondingly increased. yThe most important of all of the objects of the invention is theprovision of means for reducing the magnitude of inverse, and coupledtherewith, the object of the invention includes means for controllingsuch reduction, and means for synchronizing the reducing means with theapparatus using the useful portion of the Wave so that there will be acoordination of loads upon the apparatus one using the useful portion ofthe wave and another the inverse portion thereof so that the latter mayfunction in an increasing quantity when the load upon the apparatusenergized by the useful portion of the Wave is increased.

Another important object of the invention is to provide a relativelysimple apparatus which will perform the objects hereinabove identified.

When the invention shall have been explained and illustrated as it isillustrated in the accompanying sheets of drawings, it will at once beapparent that there may be numerous substitutions of equivalents for theseveral elements provided for carrying out the objects of the invention,and it is to be noted at the beginning that other electrical apparatusfunctioning or operating in the same way as the elements herein namedare intended to be included when the elements herein described andillustrated are referred to. It is further ldesired by the applicantthat the terminology herein found shall not only apply to the particularapparatus illustrated, describe-d and named, but shall also apply withequal force to any other electrical apparatus functioning in the sameway, operating in a like manner, or providing the same results as theelements named and described. Several forms of an apparatus embodyingthe invention, in conjunction with the illustrative diagrams', will befound in the accompanying Asheets of drawings, hereby made a part ofthis specication and in which: l

Figure 1 is a schematic diagram showing the energizing circuit for anX-ray tube of atype capable of rectifying its own current.

Figure 2 is a set of curves showing the voltage impressed across theterminals of an X-ray tube when energized in a circuit such as is shownin Figure 1.

Figure 3 is a set of vcurves showing the voltage across and currentthrough the primary of a high tension transformer such as is shown inFigure l when in an X-ray tube circuit.

Figure 4 is a schematic diagram showing a new and improved circuit forenergizing an X-ray' tube of the type capable of rectifying its owncurrent and in which a separate absorption circuit has been included forthe purpose of increasing the X-ray output from such a tube.

Figure 5 is a curve showing the voltage impressed across the terminalsof an X-ray tube when energized in a circuit such as is shown in Figure4. l

Figure 6 is a set of curves showing the Voltage across and the currentthrough the primary of 1% a high tension transformer such as is shown inFigure 4 when in an X-ray tube circuit.

Figure 7 is a schematicdiagram of a device constructed in accordancewith the invention and in which the selective portion of the absorptioncircuit consists of a mechanical rectifier driven by a synchronousmotor. y

Figure 8 is a device similar to that illustrated in Figure 7, but inwhich the synchronous rectier is replaced by a thermionic vacuum tube.

Like reference characters are used to designate similar parts in likedrawings and in the description of the invention hereinafter given.

While there is illustrated and described herein devices embodying anauxiliary secondary associated with an absorbing circuit as Vembodimentsof my invention, it is not proposed to limit the invention to thisconstruction. The broad aspects of the invention will cover anyarrangement whereby control of the inverse potential may be had, theparticular device described herein being advanced because of practicaladvantages associated therewith when applied to the X-ray art.

Another device by which the same result may be obtained is theparalleling of the useful load with an absorbing circuit, both operatingfrom the same secondary.

Other methods by which similar results are secured can be readilydetermined by any electrical engineer and the applicability of theseparticular devices to the various' arts will depend .on the specificuses to which the devices are to be put. It is not the intention tolimit the invention to a particular embodiment described herein, but toassert the novelties disclosed in the bro-adest possible terms which thepresent state of the art will permit.

As has been indicated by that which has a1- ready been said, the presentinvention has to do with a medium for increasing the useful resultsobtainable from an electrical device of a given size which is energizedfrom high tension transformer direct and which recties its own current,and it has also to do with any device which is adapted to be energizedby half the wave, and in which it is desirable tocontrol the inversepotential.

For simplifying the explanation of the invention, the figures in theseveral drawings are taken up in seriatim.

In Figure 1, the ordinary circuit used in X-ray work is shownschematically. Therein is an X-ray tube 20 which is provided with ananode 21 and a cathode 22. The X-ray tube is of the heated type,generally designated in the art as a Coolidge tube, and the cathode 22thereof is provided with a heated filament which is energized throughthe medium of a transformer 23. The transformer A23 is normally of thestep down variety and the secondary 24 thereof, which is connected tocathode 22, is insulated from the primary 25 thereof by suicientinsulation to withstand approximately one-half of the voltage across theterminals of the tube 20.

One connection between the cathode 22 and the secondary 24 is connectedto one terminal of the secondary 27 of, a high tension transformer 26which is employed for furnishing the high potential alternating currentnecessary to energize the X-ray tube 20. The other terminal of thesecondary 27 is connected in the usual manner to the anode 21 of thetube 20.

The primary 28 of the high tension transformer is energized in anysuitable manner, for instance,

through the medium of an auto transformer 29 which in turn is energizedfrom asource ofV a1- ternating current 30. 'A variable tap 31 isassociated with the auto-transformer 29 and vthrough this, means areprovided for varying the potential which is supplied to the high tensiontransformer 26. Consequently the voltage impressed across the tube 20 isvaried, controlled and regulated accordingly tothe adjustmentslofautotransformer 29. i

Variation in the heating of the filament 22 is obtainable through the`medium of any regulatory device connected within either the prima-ry orthe Ysecondary circuit of the filament transformer 23. In the particularconstruction shown, this part ofthe device comprises a variableresistance 32 in series with the primary 25 of the lament transformer 23which transformer in turn is energized from a source of energy 30. s

There is nothing new in the circuit shown in Figure l as all ofthercircuits therein arevery well known in the art andthe individualelements of the circuit are capable of various structures and methods ofconnection, all of which are equally well known.

The purpose of showing such gure is to'illustrate the usual X-raycircuit arrangement in its simplest form and to use such form as a basisfor indicating in the simplest possible manner the additional circuitsnecessary yto carry o-ut the present invention and for the additionalpurpose of showing the improvements and advantages which are obtained bythe additional circuits comprising the subject matter of thisi'nvention.

When a tube is energized in the circuit illustrated in Figure 1 and inwhich alternating current is impressed across the terminals of the tube20, the tube must select and use the alternation of correct polarity andconjointly block and reject that of inverse polarity. The potentialacross such tube 20 during the complete cycle'is shown by the curve 35in Figure 2. The alternation 36 of the curve 35 which is below thecenterline shows the rejected part of the cycle. This is 120 normallycalled inverse and, of course, results in a reverse potential across thetube. I

The alternation shown at 37 illustratesthe useful current Wave or that4portion of the cycle of correct polarity for energizing the tubewhich125 is accepted by the tube and which passes through such tube for thegeneration of X-rays. No rea'- son is apparent for discussing theoperation of va self-rectifying tube in great detail for it is wellknown how an X-ray tube selects the alternation 130 of proper polarity.This subject has formed the subject matter of a number of patentapplications and is common knowledge in the art.

Alternation 38, shown inrdotted lines in Figure 2, representsalternation 37 projected against 135 alternation 36, and shows thecomparative differences in height, amplitude, or area ofthe usefulvoltage and the inverse voltage wave.

The numeral 39 is used to indicate the diiference in height between thepeak of the useful 140 and of the rejected wave. Under normalconditions, the height of these alternations are to each otherapproximately as is to 100. In other words, it is necessary to provideinsulation inthe v high tension transformer 26 for 1,00 kilovolts for145 every 85 kilovolts used in the X-ray tube 20.

f Likewise, and in the same manner, the tube 20 must be designed in suchproportions as to withstand Vthe potential vof kilovolts for everya e5kilovolts used in energizing Such tube.' Thus, 150

it has been found necessary to the design of equipment of this natureand for given classes of work to increase their bulk andhence their costvery nearly directly in the proportion named. Therefore, the cost andbull; of equipment of this .type would be greater in the same proportionof 100l to 85.

'I he energy of the X-ray output from a tube is in proportion of thesquare of the voltage impressed thereon, hence, the output under thecircumstances noted would be therefore, as the lsquare of l85 is to thesquare of 100 or 7225 to 10,000, a difference of approximately 28 percent.

safely withstand. Likewise, one of the provisions of the presentinvention is to make it unnecessary to add insulation to transformersVfor a voltage higher than that used for a useful load.

The means whereby these results may be accomplished, graphically, are byreducing the height of alternation 36 so that it is approximately thesame or less than the height of alternation 37, or vice versa,increasing the height of 37 until it is the same as the amplitude of 36,and as has hereinbefore been stated, it is the broad object of thepresent invention to provide means for obtaining complete control of theinverse or of reducing the amplitude of such inverse to a desiredquantity equal to or less than that of the useful output of thetransformer.

As will later be shown, in the particular method disclosed within thepresent application, it is proposed to separately load the transformerby means of a selective energy absorption device to such a point thatthe height of the curve 36 of the inverse part of the wave will be thesame as the height of the curve of the loaded part of the wave, to wit,37.

Reference should now be had to Figure 4.l In this figure, there is acircuit analogous to that shown in Figure 1. Similar referencecharacters are applied thereto, and the description of the circuit shownin Figure l can be read directly upon Figure 4.V In addition, however,there is a `selective loading circuit associated therewith and in directconnection with the high tension transformer- 26.

In this embodiment of the invention, there ls a second secondary 33,herein sometimes referred to as an auxiliary secondary althoughlprobably not in a true sense an auxiliary of the main secondary of saidtransformer, associated with a selective-loading device indicated at 34.This latter device may be of any selective variety. Its function is toabsorb sufficient energy during the alternation through which the X-raytube is will permit current to pass to the loading device 34 during thealternation not used by the X-ray tube. Y

As may be readily understood, the selector may take the form ofasynchronous mechanical switch, a thermi'onic device, a vibratingpolarized relay, a cold cathode rectifier, a mercury arc rectifier, achemical rectifier, an electrostatic rectifier, or any of the deviceshaving unilateral conductivity `well known in the art. It is to beconceived that additional and better devices possessing unilateralconductivity will later be introduced and such devices, as they aredeveloped may be substituted for any of the above named, or for any oneof such devices which has been omitted from the foregoing list.

The resulting curves showing the voltage across the X-ray tube with theabsorption circuit just described, in4 operation are illustrated inFigure 5 of the drawing. In this figure, 52 represents the completepotential Wave impressed on the X-ray tube, 53 the unused alternation,and 54 the useful alternation of the wave. From a study of this figureit will be seen that the heights of the twophalves of the wave are verynearly identical or identical.

By an adjustment of the loading resistances or other device which may beemployed therefor, the relative height of these halves of waves may bealtered so that, if necessary, the unused portion of the wave may bereduced to a lower value than the used portion of the wave, or viceversa. It is apparent, at once, that by the system graphicallyillustrated in Figure 4, and hereinafter to be more completelydescribed, that there is complete mastery of the unused portion of thewave and that it may be controlled at the will of the operator to beequal to, less than or greater than the height or amplitude of theuseful portion of the wave, as is necessary, advantageous, or desired.

An additional advantage may be had from a device of the character hereindescribed in that the power factor of the energy drawn from the line issubstantially improved by the use of the absorbing circuit. This isillustrated inA Figures 3 and 6, the former, Figure 3, containing the`Voltage and current waves at the primary end of the transformer 26 inFigure 1.

In this ligure, Figure 3, represents the voltage wave across the primaryof the high tension transformer 26, the unused alternation beingdesignated 41 and the useful portion or alternation being designated 42.Y v

The current wave through the primary of the same high tensiontransformer is marked 45, the

unused portion of such wave being designated 46, and the useful portionthereof by the reference character 47.

' In Figure 6', the same wave is shown for the device illustrated inFigure 4. In said Figure 6,

the voltage wave is represented by the reference character 55, theunused portion being designated 56, and the alternation which is used by-the character 57.

The current through the primary of the transformer of Figure 4 isdesignated by the curve 60, the curve 6l shows the unused portion of thewave, and the curve 62 the useful portion. An examination of these waveshapes discloses a marked improvement in the power factor by the use ofan absorbing circuit as may be readily worked out byv a comparison ofFigure 3 with Figure 6. 7

A device such as is shown in Figure l1 has a power factor ofapproximately 47%. The same device with the absorbing circuit includedtherein shows a power factor of approximately 90%. The phase shift on`the used portion of the Wave will be seen to be approximately identicalin both Figures 3 and 6, the change in the power factor taking place` inthe unused portion of the wave.

No attempt in the foregoing description has been made to connect thesecurves with those shown in Figures 2 and 5 from the standpoint of phaseposition. Rather than resort to that, a common standard of placing theunused alternation first and below the base line has been adhered to inorder to make the curves more easily readable.

In the foregoing discussion, there has been outlined only a theoreticalconsideration involved in the present application for Letters Patent andno effort has been made to explain the general features embodying theinvention graphically disclosed in Figure 4. In that portion of thedescriptive matter following, an effort will be made to explain some ofthe practical applications of the present invention, and the descriptionthereof will be limited to two constructions. In one of these, thatshown in Figure 7, the selective portion of the absorbing circuitconsists of a mechanical rectifier actuated or driven by a synchronousmotor. In Figure 8, a similar device to that illustratedin Figure 7 isshown, but in place of a synchronous motor, there is employed athermionic tube. v Y

`In order to prevent any possibility of confusion betweenthe severalgures, the reference char- -acters employed upon Figure 7.are differentfrom those selected for the preceding figures.

Beginning with an X-ray tube, designated 67 the parts thereof are easilyrecognized. The anode is designated 68, and the cathode 69. Within the-tube and mounted in the usual manner is a lainent, which is energizedby a filament transformer 70, they filament Within the X-ray tube beingenergized by the secondary 71 of such lament transformer. The primary ofsuch filament transformer is designated 72.

Associated with the tube is a high tension transformer 73, suchtransformer having a secondary 74 used to energize the tube 67, and anauxiliary secondary designated 75 which forms a part of the absorptioncircuit, each of which secondaries is energized by a single primary 76in such transformer 73. There is disposed in the high, tension tubeenergizing circuit a milliammeter 77.

In one leg of thecircuit leading to the high tension primary 76, thereis an auto transformer 78 possessing a plurality of taps 79 each ofwhich is provided with a contact kbutton 80. The other leg of thecircuit is from one transformer directly to the other.

-In the auto-transformer 78 is a ring 81 connected to one sideof thetransformer primary 76,Y and associated with said ring 81 is a contactlever 82 which-is ladapted to swing upon a pivot 83. A plungercontact 84which is insulated from lcontact lever 82 is employed for making contactwith ring 81. A second plunger Contact 85 is insulated from contactlever 82 and is for making contact one at a time with the contact points80. Between the plunger contacts 84 and 85 is a conductoror connector86.

Associated with the circuit from the source of power to theauto-transformer 78 is a main switch 87 by which the impression ofenergy upon the auto-transformer from a source of alternating current 88is controlled.

In the present instance, there is provided an operating switch 89 forenergizing the autotransformer 78, there -being in such a switch abutton 90 employed to establish a connection with auto-transformer 78through a resistance 91. In

starting the X-ray tube in operation energize-l tion of theauto-transformer and hence ofthe tube is effected with resistance 91 incircuitfby which means a vlower potential is first impressed across thetube until the. tube is operating for a"V with the auto-transformer 78 acontact ring 95 which is connected at one side to the negativ side of aunilateral selective device.

Upon the control handle 82 of the auto-transformer there is provided aplunger contact 96 `making contact with buttons 94, and in juxtapositionthereto is asecond plunger contact 97 contacting with the ring 95.Between the plunger contact 96 and the plunger contact 97 there is aconductor or connector 98.

The selective portion of the absorption circuit is designated 99, and asecond absorption resistance in the absorption circuit is marked 100. Inassociation with the latter is a plurality of contact points 101, andthere. is a contact rail 102 connected to the other side of said device99. In the absorption circuit 99 there is also a contact lever 103 whichis mounted upon pivot 104, there being on the lever 103 contact plunger105 which is adapted to engage the points 101 one at a time and a secondcontact plunger 106 which engages the rail 102. Intermediate theplungers 105 and 106 isa connector or conductor 107.

In association with the filament transformer primary 72, there is aresistance 108 in series therewith for the purpose of regulating thepotential across the primary 72 of theY filament transformer andconjointly controlling the heating of the filament in cathode 69. Theresistancesl 108 are so arranged that they are controlled by the samehandle as is used for resistances 100.

For this purpose, there are contact points 10'9v in circuit withresistances 108, and associated'- at a time is designated 111 and aplunger Contactv engaging the rail 110 is marked 112, the connectionbetween plunger contacts 111 and 112 being `with the device is a Contactrail 110 connected to one side ofthe line from-the source `ofpowerj Aplunger Contact` engaging points 109 one the selection of thealternation to be loaded.

This is a mechanical device actuated by a synchronous motor, themechanical selector being designated 114. In such selector, there isacontact brush 115 electrically connected to rail-95,.,

and a second contact brush 116 connected to rail 102. A commutator 117is driven byva four pole the lines connected to thepower source 8,8 andwhich operates at 1800 revolutions per minute at 60 cycles, or at 75revolutionsper minute at 25 .ments 120 is marked 121.

With the apparatus arranged 'as is illustrated commutator segmentsaredesigy 14o synchronous motor 118 which is energized from in Figure 7,with each cycle of alternating current from the sourceof power 88passing through the auto-transformer 78, there is induced from theprimary 76 of transformer 73 a separate current Wave in each of thesecondaries 75 and 74.

The useful portion of the current induced in the secondary 74 is adaptedto energize the X-ray tube 67.

Without the absorbing circuit, there would be on the opposite half ofthe Wave the generation of an inverse current which could not passthrough the tube 67 which is self-rectifying, but the voltage of theinverse current Would be of greater i value as to height or amplitudethan the used or useful portion of the Wave. By setting the commutator117, so that during that period or interval of time in which there wouldbe in older methods normally impressed upon the tube the inverse justreferred to, a load is brought into circuit With the auxiliary secondary75, during which interval the resistances 93 and 109 are energized bythe electromotive force induced in auxiliary secondary 75 as an incidentto its inv- --ductive association With primary 76.

erated when there Will be a dierent potential to 'raise the peak of theinverse half of the potential wave to a height in excess of the peakwhich is attained by the useful portion of the potential Wave.

As has been before indicated, the inverse potential should be depressedor suppressed to such an extent that the peak attained thereby will notexceed the peak of the used portion of the Wave. It should suggestitself then that the resistance in the absorption circuit will have tobe varied 'according to the load upon the secondary 74.

By mathematical calculation, the amount or resistance required for anygiven load may readily be calculated, so that in the auto-transformer78, .there is supplied in association with resistance 93 buttons 94Which correspond with and are complemental to the buttons upon the taps79 in the auto-transformer, so that when any particular adjustment ofthe auto-transformer 78 is made, there Will be a corresponding increaseor decrease in the amount of resistance in the absorber circuit. Theamount of resistance in such absorber circuit will therefore, at alltimes, be sufcient to suppress the inverse to the extent that the peakof the inverse potential Wave is never greater than the peak of the usedportion of the Wave.

The hereinabove referred to compensating regulation of the resistance inthe absorber circuit relates to and has to do only with the load Whichmay be controlled through the auto-transformer. The temperature of thefilament in an X-ray tubeis adapted to control, Within limitations, theamount of energy passed thereacross and consequently the amount ofX-light generated therein. Such being the case, and it being customaryand usual to employ a filament regulator control or controls, it isnecessary and desirable to associate With such filament regulator orcontrol members, a second series of resistances lated,so that inassociation with the filament control or regulator 108 there may be aplurality of contact buttons 101 leading to such resistance in theabsorber circuit that-coincidentally with and conjointly with theregulation of the filament control member resistance will be added tothe absorber circuit or removed therefrom.

Thus the resistance inY the absorber circuit may be balancedtoapproximately that point Where there will be a suppression of inverseonly to the The inclusion of a load for the unused'portion of the Wavedestroys all of the disadvantages which have heretofore been found inproviding a transformer with a loadV comprisingl .a device adapted to beenergized only by a unilateral current, there then always being surgesor fluctuations because of the unloading of the transformer when thealternation changes to that of opposite polarity.

In Figure 8, the circuits are same as in Figure 7 save for theelimination of the synchronous motor 118 and its associated commutator.

In place of the commutator and synchronous motor, there is provided adevice adapted to be energized by a unilateral flow of current, andwhich is of such a construction that the alternation of oppositepolarity cannot pass therethrough, as for example a kenotron, or thelike. To energize such thermionic device, it is necessary to have afilament current transformer as is well known in the art.

In Figure 8, the thermionic selector is designated 122, and there is aplate 123 therein electrically connected to the rail`102. Thei'ilamentary cathode 124 in the selector 122 is electrically connectedto rail 95. For energizing the lamentary- Icathode 124 there is atransformer 125: for heating purposes, the secondary thereof beingdesig-l nated 126 and the primary 127. Such primary is energized byconduits or linesconnected to the source of power 88.

In the arrangement shown in Figure 8, the operation of the apparatus issubstantially identical 'With that described with respect to Figure 7.

auxiliary secondary 75 is unused, it being unable to pass through tube122.

When the other half portion of the Wave, that portion of oppositepolarity, is being induced in the secondary 74, current may iiovvthrough the thermionic device 122 and at this time the current inducedin auxiliary transformer 75 iiows therethrough to the several series ofresistances. The amount of energy iiowing through the device 122 andbeing absorbed by the resistances 93 and 100 is determined by the numberof turns in the resistances 93 and 100 in circuit with the thermionicdevice 122 at this particular time.

The load therefore, upon the primary '76 is made substantially constantby the alternate employment of such load, primarily for a usefulpurpose, namely, the generation of X-rays in the tube 67 upon one halfof the current wave, and upon the other half of the wave, the productionof suicient energy that the coil is required to energize the resistances93 and 100 to that extent that the peak of the inverse and the peak ofthe used portion of the wave are substantially the same.

Electrical equivalents for the mechanical rectifier and the thermionictube shown in Figures '7 and 8 respectively, may readily be found, forany suitable device having unilateral conductivity may be substitutedtherefor. Either of these devices could be replaced by a properlydesigned polarized relay, mercury arc rectifier, mechanical rectifier,chemical rectifier, electrostatic rectifier, or a cold cathoderectifier. Some rearrangement of the circuit, and the ancillary partsthereof would be necessary in the employment of each of these devices,but the new connections involved would not involve invention, as similarconstructions already exist in the art. For the adaptation of each ofthe devices for the particular purposes here outlined there must be someslight rearrangement in the circuit, the reasons and manner of suchrearrangement being well understood,

In the description, there has been shown a useful load to be an X-raytube. It is not intended that the invention is to be limited to thisparticular application for it may be `iust as readily applied to anyother device which consumes only every other alternation and in whichthe potential of the idle alternation rises above that of the usefulalternation.

In the X-ray art itself, the invention is especially applicable to thosedevices where it is necessary to prevent increase in the size of thecontainer for the high tension transformer and for the tube. suchdevices in part being illustrated in several cri-pending applications,namely, Serial No. 286.825, led June '2.9. 1928. entitled X-rayoperating table. Serial No. 285.390. filed June 14. 1928, entitled X-rayapparatus, Serial No. 285.391. filed June 14, 1928, entitled X-rayapparatus, and others.

I claim:

1. In combination, an X-ray tube, a transformer having a primary and aplurality of secondaries, a circuit including one of said secondariesand said tube, a source of power, a variable impedance, an absorptioncircuit including said variable impedance and the other of saidsecondaries, an auto-transformer, a circuit including saidauto-transformer, said source of power and said primary, a selectorswitch for closing said absorption circuit so that it may be energizedwith the half waves rejected by said X-ray tube, and a unitary controlmember interlocking said auto-transformer and said variable impedancefor conjoint adjustment.

2. A transformer having a primary and two secondaries, a source ofalternating current, a circuit intermediate said source of alternatingcurrent and said primary, a rheostat in said circuit, an X-ray tube,connections from one of said secondaries to said tube, a secondrheostat, an absorption circuit including the second of said secondariesand said second rheostat, the X-ray tube passing one half wave of eachalternation from the alternating current source, selector means incircuit with said absorption circuit for closing said circuit to passvthe other half wave of said alternating current through said secondrheostat, and interlocking control means for conjointly operating saidrheostats.

3. An electrical system comprising a circuit having a load of unilateralconductivity therein, an absorption circuit having a variable impedancetherein, a source of power, a transformer having a primary in circuitwith said source of power and two secondaries, one of said secondariesbeing in circuit with said load, the other secondary being in saidabsorption circuit, a rheostat in the circuit to the primary of saidtransformer, a selector for energizing said absorption circuit with thehalf waves rejected by said load, and means for interlocking saidrheostat and said variable impedance for conjoint predetermined relativeadjustments.

4. An X-ray system comprising a source of energy, a transformer having aprimary and two secondaries, an X-ray tube, a selector device, anauto-transformer intermediate said source of power and said primary, acircuit including one of said secondaries and said tube, a variableimpedance, an absorption circuit having said variable impedance thereinand including said second secondary and said selector device, saidabsorption circuit being closed by said selector to receive half wavesnot useful for energizing said tube, and an interlock between saidauto-trans former and said variable impedance for conjoint predeterminedadjustment.

5. An X-ray tube having a filament therein, a source of power, anauto-transformer, a main transformer having a primaryv and twosecondaries, .a circuit including said primary, said autotransformer andsaid source of power, a circuit including one of said secondaries andsaid tube, a filament current transformer, a filament circuit includingthe secondary of the filament curn rent transformer and the iilament insaid tube, a circuit from said source of power to the primary of saidfilament current transformer, a rheostat in said last mentioned circuit,a selector device, a plurality of other rheostats, an absorption circuitincluding the other of said secondaries, said plurality of rheostats andsaid selector device, said selector device causing said absorptioncircuit to receive the half waves not useful to energize said tube, andinterlocks between said auto-transformer and one of the rheostats insaid absorption circuit and the filament current transformer rheostatand the other rheostat in said absorption circuit for conjointoperation.

JULIUS B. WANTZ.

